Method for diagnosis of helicobacter pylori infection

Abstract

A rapid, non-invasive breath-test method and device for diagnosing the presence or absence of H. pylori in a subject without administration of isotopic tracers is described. The device consists of a highly sensitive colorimetric ammonia sensor placed in contact with sampled subject breath. The sensor is measured using appropriate reflection spectroscopy instrumentation. The breath-test method consists of measuring a basal ammonia level with the device, administering non-isotopic urea and continuing measurement of the ammonia content in a plurality of consecutive breaths. Diagnostic differences in breath ammonia are identified between H. pylori infected and uninfected individuals.

1. A method for detecting the presence or absence of  H. pylori  infection in an individual comprising:
 a) exposing at least one ammonia sensitive sensor to expiration of an individual, wherein where more than one sensor is exposed, the sensors are exposed to identical samples of respiration; 
 b) deriving, based on response of the at least one sensor to the exposure, a basal ammonia measure of expired ammonia over a basal measurement period; and 
 c) comparing the basal ammonia measure against a normative value that reflects at least one of a  H. pylori  positive population measure and a  H. pylori  negative population measure, wherein the  H. pylori  status of the individual is determined. 
 
   
   
     2. The method of  claim 1 , further comprising:
 a) administering a  H. pylori  urease enzyme substrate following determination of the basal ammonia measure; 
 b) deriving a post-substrate ammonia measure of expired ammonia over a post-urea measurement period of about 10 minutes to about 90 minutes after the administration of the substrate; and 
 c) comparing at least one measure of expired ammonia selected from the group consisting of the absolute measure of the post-substrate period, the absolute difference between the measures of the basal period and post-substrate period, the relative change between the measures of the basal period and post-substrate period, and, the rate of change in expired ammonia measures during the post-substrate period, against a normative value that reflects at least one of a  H. pylori  positive and a  H. pylori  negative population measures, wherein the  H. pylori  status of the individual is determined. 
 
   
   
     3. The method of  claim 2 , further comprising:
 a) administering an agent intended to increase expired ammonia either coincident or subsequent to administration of the  H. pylori  urease enzyme substrate; 
 b) deriving a post-substrate and post-agent ammonia measure of expired ammonia over a post-agent measurement period of about 10 minutes to about 90 minutes after ingestion of the substrate and agent; and 
 c) comparing at least one measure of expired ammonia selected from the group consisting of the absolute measure of the post-agent period, the absolute difference between the measure of the basal period, post-urea period and post-agent period, the relative change between the measures of the basal period, post-urea period, and post-agent period, and, the rate of change in expired ammonia measures during the basal period, post-substrate period, and post-agent period, against a normative value that reflects at least one of a  H. pylori  positive and  H. pylori  negative population values, wherein the  H. pylori  status of the individual is determined. 
 
   
   
     4. The method of  claim 3 , wherein the agent intended to increase expired ammonia either coincident or subsequent to administration of the  H. pylori urease enzyme substrate is an antacid.    
   
   
     5. The method of  claim 3 , wherein the agent intended to increase expired ammonia either coincident or subsequent to administration of the  H. pylori  urease enzyme substrate comprises about 2 g aluminum hydroxide and about 2 g magnesium hydroxide. 
   
   
     6. The method of  claim 1 ,  2  or  3 , wherein the individual undergoing testing fasts for at least 8 hours before initiation of the method. 
   
   
     7. The method of  claim 1 , wherein the at least one ammonia sensitive sensor has a sensitivity to ammonia in the range of about 0.05 ppm to about 5 ppm. 
   
   
     8. The method of  claim 1 , wherein the ammonia sensitive sensor is an optical sensor for expired ammonia, comprising:
 a solid substrate; and 
 an ammonia sensitive indicator dye having measurable spectral characteristics immobilized in or on the solid substrate so that exposure of the dye to expired ammonia causes a change in the spectral characteristics of the ammonia-sensitive indicator dye. 
 
   
   
     9. The method of  claim 8 , wherein the substrate is polytetrafluorethylene. 
   
   
     10. The method of  claim 8 , wherein the indicator dye is a non-water soluble pH indicator dye. 
   
   
     11. The method of  claim 8 , wherein the substrate is an ammonia permeable solid-phase film. 
   
   
     12. The method of  claim 10 , wherein the indicator dye is a weak acid compound that undergoes changes in its absorption spectra upon acid/base dissociation. 
   
   
     13. The method of  claim 12  wherein the weak acid compound is selected from the group consisting of bromocresol green and bromophenol purple. 
   
   
     14. The method of  claim 8 , wherein the substrate is a gas permeable hydrophobic polymer. 
   
   
     15. The method of  claim 14 , wherein the hydrophobic polymer is a substituted ethylenic polymer. 
   
   
     16. The method of  claim 8 , wherein the substrate is porous. 
   
   
     17. The method of  claim 1 , wherein comparing the basal ammonia measure in c) comprises comparing a basal ammonia measure selected from the group consisting of: an absolute value measurement; a rate of change measurement; and combinations thereof. 
   
   
     18. The method of  claim 1 , wherein where more than one sensor is exposed, the sensors are exposed to the identical respiration samples within a single chamber. 
   
   
     19. The method of  claim 1 , wherein where more than one sensor is exposed, the sensors are exposed to identical respiration samples in different chambers.